Biology subjects

Chan, R. L.

Publications and source records attributed to Chan, R. L..

12 recordsLinked to original sources

bioRxiv2026

Protein-independent regulation by transgene-derived small interfering RNAs rewires endogenous regulatory networks to enhance plant growth, architecture, and drought performance

Plants produce diverse small interfering RNA (siRNA) molecules that modulate development, environmental responses, and immunity. Although transgene-derived siRNAs are traditionally viewed as mediators of gene silencing, whether they can actively regulate endogenous host pathways remains largely unexplored. Previously obtained Arabidopsis, wheat, and soybean plants expressing the sunflower gene encoding the transcription factor HaHB4 exhibited water deficit tolerance. Here, we show that expressing inverted-repeat constructs that generate HaHB4-derived siRNAs without producing the HaHB4 protein bypasses transgenic growth penalties and instead enhances vegetative vigor and reproductive performance. In Arabidopsis, these DCL-dependent siRNA-producing lines exhibited enhanced root growth, increased stem and pith areas, increased cauline branching, and higher seed yield under both optimal and water-limiting conditions. Transcriptomic analysis revealed convergent repression of biotic stress-related genes, accompanied by increased bacterial susceptibility and reduced sensitivity to salicylic acid-mediated growth inhibition, suggesting an altered balance between immunity and growth. Functional characterization of candidate endogenous HD-Zip I targets further showed that athb20 and athb53 mutants recapitulated the increased stem expansion and cauline branching of the RNAi lines, respectively, pointing to endogenous HD-Zip I genes as candidate mediators of these traits. Remarkably, these effects were observed in newly obtained transgenic soybean plants, where expression of HaHB4-derived siRNAs enhanced vegetative vigor under controlled growth conditions. Overall, these findings show that transgene-derived siRNAs act independently of protein function to rewire endogenous regulatory networks, providing a potential strategy to optimize crop architecture and yield.

plant biology↗

bioRxiv2026

Isogenic reciprocal grafts with transgenic HaHB11 plants dissect shoot and root contributions to yield in field-grown soybean: a multi-omic study

Soybean must coordinate root and shoot signals to optimize yield. Grafting is a powerful tool to study this communication. However, most studies compare contrasting genotypes and cannot separate genotype from graft combination effects. Here we used isogenic soybean lines to dissect root and shoot contributions in the field. These lines differ from controls in a single gene, either HaHB11 or HaHB4, two sunflower HD-Zip I transcription factors associated with increased grain number. Unexpectedly, heterografted plants outperformed homografts in several yield-related traits, an effect not previously documented in soybean. This advantage was reproduced with both HaHB11 and HaHB4 scions, suggesting the effect is not gene-specific. Under non-stress conditions the scion governed yield-related traits, particularly pod number, as well as the leaf transcriptome, whereas both organs left subtle metabolic signatures. The root contribution was minor and confined to the R6-R7 transition, where it was specific to HaHB11. The highest-yielding combination was a control rootstock with an HaHB11 scion (CH11), which increased grain number by [~]30% over the best homograft. CH11 showed higher stomatal conductance and lower leaf temperature; yet CH11 and HaHB11 homografts were remarkably similar, sharing higher stomatal density, differing in only four leaf-expressed genes, and lacking a metabolomic signature. Thus, under non-stress conditions, soybean grain number is governed by the scion and the graft combination, and accompanied by early physiological differences rather than by leaf molecular reprogramming.

plant biology↗

bioRxiv2026

Mechanical stress modulates source-to-sink partitioning and drought response in Arabidopsis

Mechanical stimuli provoked by wind, soil compaction, rainfall, and biotic interactions strongly influence plant phenotype, growth, and development. Previous studies indicated that weight-treated Arabidopsis thaliana plants increase stem diameter, vascular bundle number, and seed yield, involving auxin, brassinosteroid, and strigolactone-related genes. In this work, we investigated how the mechanically induced increase in phloem area improves source-to-sink partitioning, while the increase in xylem area negatively affects long-term drought tolerance. Transcriptomic profiling confirmed a large-scale reprogramming of drought-responsive genes in treated plants. Moreover, quantification of sucrose and starch content highlighted an enhanced synthesis and carbohydrate transport, which ultimately and positively impacted lipid and protein contents in seeds. Using loss-of-function mutants, we demonstrate that the phloem loader SUC2 and exporters SWEET11, 12, and 16 are essential for the yield gains triggered by mechanical stress. Furthermore, mechanical treatment alters sugar metabolism. Overall, our findings indicate that weight treatment elicits a complex physiological response, in which sucrose transporters and starch metabolism play a crucial role in mediating its positive effects on seed quality and yield. Significance statementMechanical cues are ubiquitous in natural environments, but their impact on plant carbon allocation and yield remains poorly understood. This study reveals that mechanical stress reshapes vascular architecture and carbohydrate transport, enhancing source-to-sink partitioning and seed quality in Arabidopsis. By identifying sucrose transporters and sugar metabolism as key mediators of mechanically induced yield gains, our findings provide mechanistic insight into how physical forces integrate with metabolic regulation influence plant productivity.

plant biology↗

bioRxiv2024

Mechanical stress induces anatomical changes, tomato early flowering, and increased yield involving ethylene and auxins

Plants have evolved mechanisms to perceive and face mechanical stress (MS) caused by physical forces, including compacted soils, winds, rain, pathogens, and interactions with animals and plants. Previous research indicated that applying mechanical treatment (MT) to Arabidopsis increases both xylem area and seed yield. To explore sustainable tomato production, we applied MT - combining stem bending, weighting, and particular touching - to 10-day-old seedlings, using a specific weight on the upper stem for 48 h. Two days after the treatment, we observed stem enlargement and increased the number of xylem vessels and area in MT plants. Additionally, we noticed earlier flowering, leading to increased tomato production. The transcriptome of MT-treated plants revealed significant changes in the expression of several essential genes involved in central metabolism, growth responses, and crucial phytohormone signalling. By studying different tomato mutants in the ethylene and auxin signalling pathways, we demonstrated that both hormones play essential roles in the plant responses to combined MT. Our findings suggest that combined MT generates a beneficial MS in tomato plants that induces plant morphoanatomical changes that promote early flowering and increased yield, providing a promising strategy for sustainable agriculture. HighlightA combined mechanical treatment applied to tomato seedlings enhances stem width, increases the number of vascular bundles, promotes early flowering, and improves fruit yield, involving auxin and ethylene pathways.

plant biology↗

bioRxiv2024

Introgression of the sunflower HaHB4 gene in modern wheat: An advancement in resilience to deal with climate change

Breeding for improved tolerance to water deficit is critical to mitigate climate change impact on wheat yield. In 2020, Argentina approved the first wheat transformed with the sunflower HaHB4 gene (INDOO412-7), which increased yield by 16% compared to the non-transformed parental Cadenza under drought conditions. Previous studies may have overestimated HaHB4 benefits, as Cadenza is a long cycle for the Pampas region. Quantifying the yield advantage of HaHB4 in modern, well-adapted cultivars and elucidating the physiological processes involved, is crucial for identifying optimal environments for this technology. In a broad network of experiments (one greenhouse and 29 field environments), an HaHB4-introgressed line of Algarrobo was compared with the conventional cultivar. Under water deficit during the reproductive phase, the yield advantage of HaHB4 was 15% in the greenhouse and 13% in the field. HaHB4 improved the relative yield by 0.06 to 0.08 % per mm of water deficit. The enhanced water use and water use efficiency conferred by HaHB4, allowed maintaining growth and yield under water deficit. HaHB4 showed the highest benefit with moderate heat stress ({sum}Tmax > 30 {degrees}C [~]40-60 {degrees}Cd). In areas prone to drought combined with heat stress, HaHB4 would enhance yield stability by improving water-limited yield. HighlightsHaHB4-introgressed wheat enhanced water-limited yield by maintaining the crop growth under moderate to severe water deficit combined with mild heat stress through increasing water use and water use efficiency.

plant biology↗

bioRxiv2024

Field-tested HaHB11 and HaHB4 soybean exhibit increased grain number and heat tolerance at the reproductive stage

Soybean is one of the primary sources of vegetable oil and protein worldwide. However, its yield improvement has lagged behind the other major crops. This study explored the potential of the sunflower transcription factor HaHB11 to enhance soybean yield and heat stress tolerance. We generated transgenic soybean plants expressing HaHB11 and evaluated their performance across four field trials. The HaHB11 plants showed a significant increase in grain number per plant compared to controls, which can be related to an increased number of nodes and pods per plant. Flowering dynamics analysis revealed delayed blooming and an increased number of flowers per node, leading to a higher pod set, particularly between nodes four and six. Principal component analysis across field trials identified temperature as a crucial factor influencing grain number, enhancing the differences exhibited by HaHB11 plants. The pollen from transgenic plants germinated better, and tubes were longer than controls under heat stress. Carbohydrate distribution analyses indicated differential allocation of nutrients, supporting the increased pod and grain set in HaHB11 plants. Additionally, vegetation indices can distinguish HaHB11 plants from controls in several developmental stages. These results indicated that HaHB11 enhances soybean yield under heat stress, becoming a promising technology for soybean improvement. HighlightSoybean transformed with the sunflower gene HaHB11 was tested in the field for four campaigns, showing differential allocation of nutrients, increased number of nodes, pods, grains, and heat tolerance.

plant biology↗

bioRxiv2024

RSL4 regulatory network acts as an early driver of root hair growth at low temperature in Arabidopsis thaliana

The root hair (RH) cells can elongate to several hundred times their initial size, and are an ideal model system for investigating cell size control. Their development is influenced by both endogenous and external signals, which are combined to form an integrative response. Surprisingly, a low temperature condition of 10{degrees}C causes an increased RH growth in Arabidopsis and in several monocots, even when the development of the rest of the plant are halted. Previously, we demonstrated a strong correlation between the RH growth response and a significant decrease in nutrient availability in the medium under low temperature conditions. However, the molecular basis responsible for receiving and transmitting signals related to the availability of nutrients in the soil, and their relation to plant development, remain largely unknown. In this study, we have discovered two antagonic gene regulatory networks (GRNs) controlling RH early transcriptome responses to low temperature. One GNR enhances RH growth and it is commanded by the transcription factors (FTs) ROOT HAIR DEFECTIVE 6 (RHD6), HAIR DEFECTIVE 6-LIKE 2 and 4 (RSL2-RSL4) and a member of the homeodomain leucine zipper (HD-Zip I) group I 16 (AtHB16). On the other hand, a second GRN was identified as a negative regulator of RH growth at low temperature and it is composed by the trihelix TF GT2-LIKE1 (GTL1) and the associated DF1, a previously unidentified MYB-like TF (AT2G01060) and several members of HD-Zip I group (AtHB3, AtHB13, AtHB20, AtHB23). Functional analysis of both GRNs highlights a complex regulation of RH growth response to low temperature, and more importantly, these discoveries enhance our comprehension of how plants synchronize the RH growth in response to variations in temperature at the cellular level. Significance StatementRoot hair (RH) cells may expand hundreds of times, making them a useful cell size model. Integrated endogenous and exogenous cues affect their development. Even when plant development ceases, Arabidopsis and other monocots grow RH at 10{degrees}C. We previously established a strong correlation between growth response and a substantial medium nutrition reduction at low temperature. Receiving and transmitting soil nutrient signals and their impact on plant development are unknown molecularly. Our study identified two opposing gene regulatory networks (GRN) that govern early transcriptome responses linked to RH growth at low temperature. Functional analysis shows a complex regulation of the transcriptional cascade to influence the low-temperature RH growth. These results explain how cells coordinate RH formation in response to temperature.

plant biology↗

bioRxiv2022

A complex tissue-specific interplay between the Arabidopsis transcription factors AtMYB68, AtHB23, and AtPHL1 modulates primary and lateral root development and adaptation to salinity

O_LIAdaptation to soil is a well-regulated process vital for plant life. AtHB23 is a homeodomain-leucine zipper I transcription factor (TF), previously revealed as crucial for plant survival in front of salinity conditions. We wondered whether this TF has partners to achieve this essential function. C_LIO_LIA TF cDNA library screening, Y2H, BiFC, and CoIP assays were complemented with expression analyses and phenotypic characterizations of silenced, mutant, overexpressor, and crossed plants in normal and salinity conditions. C_LIO_LIWe revealed that AtHB23, AtPHL1, and AtMYB68 interact with each other, modulating root development and salinity response. The encoding genes coexpress in specific root tissues and developmental stages. In normal conditions, amiR68 silenced plants have less initiated roots, the opposite phenotype to that showed by amiR23 ones. AtMYB68 and AtPHL1 play contrary roles in lateral root elongation. Under salinity, where AtHB23 plays a crucial positive function, AtMYB68 cooperates with it, whereas AtPHL1 obstructs its action impacting survival ability and supporting the complex interaction between AtHB23, AtPHL1, and AtMYB68 in the primary and lateral roots. The root adaptation capability was associated with the amyloplast state. C_LIO_LIWe identified new molecular players that through a complex relationship determine Arabidopsis root architecture and survival ability in salinity conditions. C_LI

plant biology↗

bioRxiv2022

Source to sink partitioning is altered by the expression of the transcription factor AtHB5

Carbohydrates are transported from source to sink tissues. The efficiency of such transport determines plant growth and development. The process is finely regulated, and transcription factors are crucial in such modulation. AtHB5 is a homeodomain-leucine zipper I transcription factor, repressed during stem secondary growth. However, its function in this developmental event was unknown. Here, we investigated the expression pattern and role of AtHB5. AtHB5 localized in conductive tissues: roots, hypocotyls, stems, pedicels, and central leaf veins. Mutant plants exhibited wider and more lignified stems than controls, whereas overexpressors showed the opposite phenotype. Cross-sections of athb5 mutant stems showed enlarged vascular bundle, xylem, phloem, and petiole areas, whereas AtHB5 overexpressors exhibited callose deposits. Several genes involved in starch biosynthesis and degradation had altered transcript levels in athb5 mutants and AtHB5 overexpressors. Rosette and stem biomasses were enhanced in athb5 mutants, positively impacting seed yield and lipid content. Moreover, these effects were more evident in debranched plants. Finally, the transport to roots significantly slowed down in AtHB5 overexpressors. Altogether, the results indicated that AtHB5 is a negative modulator of sucrose transport from source to sink tissues, and its overexpression diminished plant biomass and seed yield. HighlightThe homeodomain-leucine zipper transcription factor AtHB5 is expressed in different tissues along the life cycle, repressing carbohydrate transport from source to sink and promoting callose and lignin deposition. AtHB5 mutants exhibit physiological differences with the wild-type, impacting seed yield and lipid content.

plant biology↗

bioRxiv2021

The transcription factor AtHB23 modulates starch turnover for root development and plant survival under salinity

AtHB23 is a homeodomain-leucine zipper I transcription factor, previously characterized as a modulator of lateral root initiation and higher-order roots development. The role of this gene in response to salinity stress was completely unknown. To elucidate the role of AtHB23 in response to salinity stress, we combined histochemical {beta}-glucuronidase (GUS) analysis, root phenotyping, starch staining, optic and electronic transmission microscopy, expression studies by RT-qPCR, and transcriptome analysis of silenced, overexpressor, and crossed plants. We revealed that the expression pattern of AtHB23 is regulated by NaCl in the main and lateral roots, affecting the root phenotype. A severe reduction in primary root length, a significant increment in the initiation of lateral roots, and a low survival rate in salinity conditions were observed in AtHB23-silenced plants, whereas AtHB23 overexpressors showed the opposite phenotype. These developmental defects were explained by the degradation of starch granules and an alteration in starch metabolism. The AtHB23-target gene LAX3 is repressed in the tip of the main root and affected by NaCl. We conclude that AtHB23 is vital for plant survival and adaptation to salt stress conditions, and its function is related to the gravitropic response mediated by starch granule turnover, involving the auxin carrier LAX3. HighlightThe transcription factor AtHB23 is crucial for plant survival and adaptation to salt stress conditions, and its function is related to the gravitropic response mediated by starch-granule turnover, involving LAX3.

plant biology↗

bioRxiv2021

HaHB11 transformed maize has improved yield under waterlogging and defoliation in control and field conditions

HaHB11 is a sunflower transcription factor previously described as conferring improved yield to maize hybrids and lines. Here we report that transgenic HaHB11 maize lines exhibited a better performance funder waterlogging, both in greenhouse and field trials carried out during three growth cycles. One of these trials was particularly affected by a strong storm during flowering, causing severe defoliation. Controlled defoliation assays indicated that the transgenic genotypes were able to set more grains than controls. Hybrids were generated by crossing B73 HaHB11 lines with the contrasting Mo17 lines and tested in the field. These hybrids exhibited the same beneficial traits as the parental lines when compared with their respective controls. Waterlogging tolerance coursed via the root architecture improvement, including more xylem vessels, reduced tissue damage, less superoxide accumulation, and altered carbohydrate metabolism compared to controls. Multivariate analyses corroborated the robustness of the differential traits observed. Furthermore, canopy spectral reflectance data, computing 29 vegetation indices associated with biomass, chlorophyll, and abiotic stress, helped to identify genotypes as well as their growing conditions. Altogether the results reported here indicate that this sunflower gene constitutes a suitable tool to improve maize plants for environments prone to waterlogging and/or wind defoliation. One sentence summaryPhenotyping and big data analyses indicate that the transcription factor HaHB11 confers waterlogging and defoliation tolerance, and increased yield to maize lines and hybrids in all tested conditions.

plant biology↗

bioRxiv2019

Successful field performance in dry-warm environments of soybean expressing the sunflower transcription factor HaHB4

Soybean yield is limited primarily by abiotic constraints. No transgenic soybean with improved abiotic-stress tolerance is available in the market. We transformed soybean plants with genetic constructs able to express the sunflower transcription factor HaHB4, which confers drought tolerance to Arabidopsis and wheat plants. One line (b10H) carrying the sunflower promoter was chosen among three independent lines because it exhibited the best performance in seed yield (SY). Such line was evaluated in the greenhouse and in twenty-seven field trials developed in different environments of Argentina. In greenhouse experiments, transgenic plants showed increased SY under stress conditions together with wider epycotyl diameter, enlarged xylem area and enhanced water use efficiency than controls. They also exhibited enhanced SY in warm-dry field conditions. This response was accompanied by the increased in seed number that was not compensated by the decreased in individual seed weight. The transcriptome analysis of plants from a field trial with maximum SY difference between genotypes indicated an induction of genes encoding redox and heat shock proteins in b10H. Collectively, our results indicate that soybeans transformed with HaHB4 are expected to have reduced SY penalization when cropped in warm-dry conditions, which constitute the best target environments for this technology. HighlightSoybean transformed with the sunflower gene encoding the transcription factor HaHB4 was evaluated in greenhouse and field trials. Transgenic plants significantly outyielded controls in drought-warm environments due to, at least in part, increased seed number, xylem area, and water use efficiency as well as to the induction of genes encoding redox and heat shock proteins.

plant biology↗